Where to get shielding paint cheap?

[Hopkins]

How did it work out, Hopkins? Did the resistance come down to something reasonable when it dried? Megaohms is too much. A few hundred ohms would be okay. The Super Shield Nickel measures only one or two ohms.

I've been thinking about buying some copper powder and trying to mix it into the clear Varathane that I use for all my regular painting. Dedicate one old cheapo spray gun just for the shielding spray.

The copper powder is available on Amazon and isn't too expensive:
http://www.amazon.com/Copper-Powder...&qid=1447541200&sr=8-6&keywords=copper+powder

If my mental calculations are correct, 1 lb of copper would make a pretty good supply of shielding paint?

Hey Bruce, I will let you know tomorrow, I had to leave for the weekend and didn't have time to wait for the second coat to completely dry. The resistance was dropping pretty rapidly as it was drying, and it was nowhere close to dry last time I checked. I am pretty optimistic about it.

 

[ddtkills]

Hopkins, Could you please post a pic when its dry? I am curious how it looks in the electronics/pickup cavities. I always liked the look and function of copper tape over the look and function of graphite paint. I wonder how this will compare.

 

[Hopkins]

Well, the experiment with the weld through primer turned out to be a failure. Now that it is totally dry I am not getting any conductivity at all across even the smallest span. I am guessing the solvents in the paint were the only thing making a connection, but I don't really understand why resistance was dropping as it was drying.

Tomorrow I think I will try the magnetic paint.

 

[walterw]

Well, the experiment with the weld through primer turned out to be a failure. Now that it is totally dry I am not getting any conductivity at all across even the smallest span.

hmm, just as well; time is money, and the MG nickel stuff is dry and ready to go, with less than like 20Ω from one end of a control cavity to the other after one coat, in five minutes.

to paraphrase scarlett o'hara, "as god is my witness, i'll never suffer through laborious copper foil or messy, inferior graphite brush-on paint again."

 

[Rano Bass]

I have used this with good results http://www.amazon.com/MG-Chemicals-..._UL160_SR118,160_&refRID=0YRMF24GY1QH2QD53FN3

 

[Means2nEnd]

I bought a small can from Stew Mac and I have done at least 15 instruments and haven't used a third of the can yet. Unless you are building 50 instruments a year I can't understand the need for it to be cheaper maybe that's just me though.. I do all the pickup cavities and control cavity and then I use the Stew Mac tape for just the bottoms. I solder a wire from the pickup cavities to the control cavity and it works beautifully never had noise or an issue..

 

[mansjasont]

I bought a small can from Stew Mac and I have done at least 15 instruments and haven't used a third of the can yet. Unless you are building 50 instruments a year I can't understand the need for it to be cheaper maybe that's just me though.. I do all the pickup cavities and control cavity and then I use the Stew Mac tape for just the bottoms. I solder a wire from the pickup cavities to the control cavity and it works beautifully never had noise or an issue..

I think the problem is for people like me who have built one or two instruments. It's expensive to order that from stew Mac and ship it for 1 instrument.

 

[DiabolusInMusic]

I bought a small can from Stew Mac and I have done at least 15 instruments and haven't used a third of the can yet. Unless you are building 50 instruments a year I can't understand the need for it to be cheaper maybe that's just me though.. I do all the pickup cavities and control cavity and then I use the Stew Mac tape for just the bottoms. I solder a wire from the pickup cavities to the control cavity and it works beautifully never had noise or an issue..

I think the problem is for people like me who have built one or two instruments. It's expensive to order that from stew Mac and ship it for 1 instrument.

It costs me $50 for one spray can, which does 5-10 basses, instead of the $50+ for the Stew-Mac can. The Stew-Mac stuff is also low grade paint that flakes off really easily. I don't think theStew-Mac resistance is as good as the MG Stuff either. (which will go well below 20 ohms @walterw )

 

[walterw]

The Stew-Mac stuff is also low grade paint that flakes off really easily. I don't think theStew-Mac resistance is as good as the MG Stuff either. (which will go well below 20 ohms @walterw )

yup;

the stew-mac paint smudges and gets everywhere when you touch it even the next day, and one thick coat might get you like 500Ω or even several kΩ across a control cavity. (one cheat i learned from a john suhr post is to hit the graphite gunk with a heat gun to speed up the dry time, but it's still slow and messy.)

also, the MG nickel stuff is made for plastic, so spraying the inside of a cavity coverplate works beautifully (tape off the edges and the screw holes).

it ain't even close which one is better.

 

[Means2nEnd]

I'm not arguing use whatever works for you. I bought a 1/2 pint $32 and it could do I'm guessing 40-50 instruments easily it has never flaked off anything I have painted it with and I know it does what it supposed to and does it well for under a buck a bass. The less stuff I spray in my shop the happier I am. But by all means you have to figure out what works best for you and does the job correctly at a price that makes sense for you. I was just trying to offer a different perspective.

 

[DiabolusInMusic]

yup;

the stew-mac paint smudges and gets everywhere when you touch it even the next day, and one thick coat might get you like 500Ω or even several kΩ across a control cavity. (one cheat i learned from a john suhr post is to hit the graphite gunk with a heat gun to speed up the dry time, but it's still slow and messy.)

also, the MG nickel stuff is made for plastic, so spraying the inside of a cavity coverplate works beautifully (tape off the edges and the screw holes).

it ain't even close which one is better.

Shut. The. Front. Door.

I still use copper tape on my covers and guards but I will try some paint next time.

 

[DiabolusInMusic]

I'm not arguing use whatever works for you. I bought a 1/2 pint $32 and it could do I'm guessing 40-50 instruments easily it has never flaked off anything I have painted it with and I know it does what it supposed to and does it well for under a buck a bass. The less stuff I spray in my shop the happier I am. But by all means you have to figure out what works best for you and does the job correctly at a price that makes sense for you. I was just trying to offer a different perspective.

You can get MG in paint form, you don't have to get it as an aerosol.

If you are concerned with cost you can always use aluminum tape as well. I used to do 5+ basses for under $5. It is a pitch to solder to and no conductive adhesive though.

 

[Means2nEnd]

Thanks DiabolusinMusi, cost is not a factor for me. When my can runs out I might try another product but I do like it in a non spray and I like the Stew Mac stuff being water based it's easy to clean. I hate aluminum tape not sure why I just think it looks crappy but the MG product in paint form I will look into that.

 

[walterw]

cost is not a factor for me. When my can runs out I might try another product but I do like it in a non spray and I like the Stew Mac stuff being water based it's easy to clean.

not to over-evangelize for the nickel spray stuff, but even spending the 5 minutes to tape-mask up the area, then walking outside to spray it, by the time you walk back inside it's just about dry, and there's nothing to clean up if you masked right. with all that it takes less time than using the graphite brush paint, and again it offers orders of magnitude better shielding conductivity.

heck, if you bother to wait 5 minutes and then go spray another coat you'll get it down to copper foil conductivity! (i don't, it's already way good enough after one thin coat.)

 

[Hopkins]

Well, I gave a can of this stuff a try, It does work as advertised, a magnet will stick to it, but it has no conductivity across any span. I am not sure how that is even possible as it has to have some sort of ferrous metal in the paint and I am not aware of a single one that is not conductive. It has to have something to do with the acrylic it is suspended in. I am done experimenting with alternatives, when overall the nickle stuff is not excessively expensive in the first place. It was more for curiosity than monetary reasons anyway.

 

[Bruce Johnson]

Hey Hopkins;

Before you throw your test samples away, try one more test: Sand a little bit on two spots a little distance away from each other. Then see if you get conductivity between the spots. It's possible that the base paint on both of these paints is skinning over the top, making an insulating layer. The question is whether the metal particles down in the paint are conducting with each other.

I think that's the overall situation. Any of these paints have to have a high enough percentage of metal (or graphite) mixed in, in order to reach conductivity.

Like you, I'm surprised that the magnetic paint isn't conductive. You'd think that it would have plenty of iron powder in it.

Thanks for testing these out! It adds to our knowledge base.

 

[Hopkins]

Hey Hopkins;

Before you throw your test samples away, try one more test: Sand a little bit on two spots a little distance away from each other. Then see if you get conductivity between the spots. It's possible that the base paint on both of these paints is skinning over the top, making an insulating layer. The question is whether the metal particles down in the paint are conducting with each other.

I think that's the overall situation. Any of these paints have to have a high enough percentage of metal (or graphite) mixed in, in order to reach conductivity.

Like you, I'm surprised that the magnetic paint isn't conductive. You'd think that it would have plenty of iron powder in it.

Thanks for testing these out! It adds to our knowledge base.

No problem Bruce,

I tried sanding into the finish and still no dice. The only thing I can think of is the substrate the particles are suspended in encapsulate and segregate the particles.

I will give the Martha Stewart brand magnetic paint and see if it works any better, being as the spray can is solvent based, and the brush on type is water based. I may try to see if it will spray through a prevail sprayer.

 

[walterw]

Not sure magnetic paint is what we even want here; it seems like metals that are magnetically attractive tend to be less electrically conductive.

Besides, think of ceramic magnets; plenty of attraction, but I don't think they conduct at all. The magnetic paint may not even be metal.

 

[Bruce Johnson]

Walter;

The "magnetic" paint that Hopkins is testing isn't itself magnetic. It's just paint that magnets will stick to. It's paint with a bunch of iron filings floating in it. Our thinking was that it should work as shielding. Iron isn't quite as good a conductor of electricity as copper, but it certainly conducts. And that's all you need for shielding. Our thinking was that, if they put in enough iron filings that magnets will stick to it, then it should be enough to be conductive. But, I guess not.

There must be some saturation point with mixing any of these metals in the base paint; where the particles touch each other enough to achieve conductivity. I'm going to get some of the copper powder and experiment with mixing it into the water-based Varathane that I use.

 

[Hopkins]

Walter;

The "magnetic" paint that Hopkins is testing isn't itself magnetic. It's just paint that magnets will stick to. It's paint with a bunch of iron filings floating in it. Our thinking was that it should work as shielding. Iron isn't quite as good a conductor of electricity as copper, but it certainly conducts. And that's all you need for shielding. Our thinking was that, if they put in enough iron filings that magnets will stick to it, then it should be enough to be conductive. But, I guess not.

There must be some saturation point with mixing any of these metals in the base paint; where the particles touch each other enough to achieve conductivity. I'm going to get some of the copper powder and experiment with mixing it into the water-based Varathane that I use.

I think the water-based material that the conductive material is suspended in is the key. Both of the products I tested are solvent based acrylic paints. The MSDS for the Nickle Super Shield only shows hazard information for the aerosol gas, it doesn't list any kind of solvents at all so I am assuming it is water based as well. I am going to try the water based brand of the magnetic paint, it is cheap enough, and I really just want to test my theory